1. Field of the Invention
This invention relates to liquid level sensors.
2. Description of the Prior Arts
Storage tank liquid level sensors of various types utilizing a float which floats on the surface of the liquid have heretofore been proposed. In U.S. Pat. No. 3,283,578 to Moore, for example, an outer magnet carried in a float surrounds a tube which contains an inner magnet mounted on a continuous tape. The tape is provided with visual markings to indicate the level of liquid in the tank.
A similar device is disclosed in U.S. Pat. No. 3,555,905 to George, however instead of visual markings on a tape George drives a potentiometer which is coupled to a meter for providing a continuous reading of the level in the tank.
U.S. Pat. No. 2,054,212 to Bacon discloses apparatus wherein a float drives a drum on which visual level markings are presented.
U.S. Pat. No. 3,162,044 describes a system in which a float hanging from a chain rotates a pulley which is connected to encoding cylinders provided with spaced magnets. The magnets are read by pickup heads and signals from these pickup heads are transmitted to recording heads which record indications of liquid level on magnetic tape.
In the patent to Mayes, U.S. Pat. No. 3,078,715, photocells are used to read a coded tape and present a coded signal indicative of tank level. However, the system disclosed by this patent is incapable of continuous monitoring of tank level, but must be actuated each time a reading is desired.
None of the foregoing patents provides continuous and accurate monitoring of liquid levels in a tank, combined with storage of the liquid level data and means for selectively presenting a visual output of liquid level data at a remote location. Nor do any of these patents disclose any means by which an indication of low level of the liquid can be provided, nor any means for indicating an excessive amount of water in a gasoline storage tank.